Hi Melissa...
It's not too bad thus far. Just a few things to make note of.
First is that if the focus is to be on the rider, then the fore/background elements need to be de-focused to some degree (i.e. blurred).
The mud should be blurred the most, the sky just a bit.
Also... don't make the mud look so perfect. Mud splashes are very random/chaotic looking. Your looks more like an overhead view of the dirtbike track layout.
You have a nice effect on the mud. Keep that.
I suggest you duplicate this document to try these things out.
See if this helps any and get back to us. :B